She first encountered science fiction fandom as Bjo Wells at ChiCon, the 1952 World SF Convention in Chicago. As Arnie Katz relates the story, she didn't like what she saw and was headed out the door when she ran into Shelby Vick, editor of Confusion, who soon changed her opinion of the event now that she had found a friendly face.

By the late 1950s, she had brought together a group of LASFS members to form a repertory company called Unicorn Productions which made two fan films for conventions written by Lee Jacobs, called The Genie and The Mesquite Kid Rides Again, in which she costarred with Forrest J. Ackerman, Karen Anderson, Charles Burbee, Terry Carr and Miri Carr. In 1979, she appeared in a uncredited role as a crew member in the movie Star Trek: The Motion Picture, and in 1981 in the short film Superbman: The Other Movie.

Her first involvement with fanzines came when she and husband John Trimble began co-editing Shangri L'Affaires, the official publication for the Los Angeles Science Fantasy Society (LASFS), for the years 1960 and 1961.

In 1960, Bjo Trimble initiated and directed "Project Art Show", the first art show to be included at a science fiction convention. It was in connection to promoting these art shows that she released her International Science Fantasy Art Exhibition Bulletin fanzine. Contributing artists to "Project Art Show" included Karen Anderson, George Barr, Cynthia Goldstone and Don Simpson. "Project Art Show" was a success, and lead to art shows becoming a regular feature at conventions.